The aforementioned copending applications and patents are concerned with low-temperature deposition processes, and apparatus for carrying out the processes, whereby the deposited material can be derived by striking an arc between electrodes in an evacuated space at relatively high currents and low voltages to vaporize a substance from one of these electrodes.
That substance may, in turn, be deposited upon a surface or that substance may react with other elements or substances present in the remaining atmosphere within the evacuated chamber, or with substances from the other electrode or from other electrodes to produce compounds, such as ceramics, which can be deposited upon substrates.
Frequently, however, it is desirable to obtain penetration of deposited materials significantly into the depth of a porous body or, in an appropriate case, to fill the pores or interstices of a body with a deposited material.
A specific case in which depositing a material in deep intersticial spaces is of advantage, is the plugging of a pipe in which the interstices may be cracks, macropores, microporous structures or the like.
Naturally, even prior to the arc vapor deposition techniques disclosed in the earlier applications and patents, there were attempts to deposit materials of a considerable depth within a substrate. For example, attempts have been made to utilize chemical vapor deposition or electroless or chemical plating techniques for this purpose and even to use electrodeposition techniques.
By and large these techniques have failed partly because deposits form rapidly on the regions closest to the source of the deposited material and prevent further penetration of the material. Most earlier techniques, moreover, are incapable of substantially completely filling the pores of porous bodies or structures and have not proved to be satisfactory for that reason.